Environmental and Legal Contingencies (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Commitments and Contingencies Disclosure [Abstract]
Environmental-related capital investments	$ 1.0	$ 1.7	$ 4.5
Environmental compliance costs	$ 101.6	$ 106.4	$ 118.7

Payments for operating costs to comply with environmental regulations including pollution control costs

No definition available.

Name:	aks_EnvironmentalComplianceCosts
Namespace Prefix:	aks_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration